Watts in the water.

But at the International Tidal Energy Summit awards in London, Edlund received the endorsement of his peers. After apologizing for standing between the diners and their pudding, he accepted the award for most promising turbine design. In this field, that’s not a Miss Congeniality award—it’s the real deal. Because at this stage of the industry’s development, promise is still pretty much all there is, despite grand plans and sometimes juicy incentives.

IV. A Medley of Marine Solutions

Nine years ago, the government of Scotland announced the creation of the Saltire Prize—a kind of XPRIZE of the sea. The competition promised £10-million (US $12.6-million) to the first company to create a viable marine-energy system and demonstrate it in Scottish waters. (Viable meaning at least 100 gigawatt hours of power over a two-year period.) There was a lot of hype. Then-prime minister Alex Salmond hailed Scotland as “the Saudi Arabia of tidal power” and claimed it has the potential to match the wealth created by North Sea oil.

At the time, Fraenkel ran the numbers at Marine Current Turbines. “We tried to figure out if there was any way we could win it, and we decided there wasn’t,” he says. “To build the size of project you’d need to win the Saltire Prize, you’d probably have to spend £80- to £100-million. In which case £10-million is a drop in the bucket.” It’s now clear that nobody is going to win it, at least not as originally conceived. The Saltire Prize’s website now admits that “the path to commercialization is taking longer and proving more difficult than anyone initially expected.”

You could argue that there’s just not enough chicken on this bone, period. The technology is so inefficient, the costs so high, the risks so prohibitive, that marine energy just isn’t worth it.

Of the vast potential energy of the ocean, only a very small fraction is practically extractable, says Vaclav Smil, an environmental scientist at the University of Manitoba and author of the book Energy Transitions. Tidal energy, for example, is a three-terawatt resource, yet only about 60 gigawatts’ worth lies within a transmission cable’s reach of shore. That amounts to one-third of one percent of global primary energy—“hardly a notable contribution,” says Smil. “Installing triple-glazed windows and universal use of LEDs would save vastly more energy than will ever be extracted from the ocean,” he added in an email.

So if that Eeyore-ish estimate is even in the ballpark, the question is, why do this? If the sea is so reluctant to give up its treasure, why should we even bother with it?

Here’s one answer: because we have to think of energy differently now. The low-hanging fruit will soon be gone. All the other options are going to be more challenging. What will make or break the case for each of them is not so much what they are as where they are.

“Until storage gets exceedingly cheap, or social license is such that you can build wind turbines and giant hydro dams everywhere—and I don’t see that happening—you need a suite of all these different technologies,” says Bryson Robertson, a mechanical engineer at the University of Victoria-affiliated West Coast Wave Initiative in British Columbia. Blanketing the Sahara with solar panels may be the cheapest way to do renewable energy right now, but it’ll never be the answer in a temperate rainforest. Where there’s a mountain, you tap the streams spilling down it with run-of-river projects. Where there’s a pinch point in the coastal landscape, you steal energy from the tide. You buy what the Earth is selling, where it’s selling it. Indeed, to try to choose the best among renewable energy sources is as ridiculous as going all in with a single vitamin in your diet, says Stephen Salter. What’s needed is a bit of fusion cooking.

Off the coast of Argentina, a company called SeatechEnergy is making fuel from seaweed. Grown in vast farms in high-productivity zones, the seaweed is digested into natural gas, which is convertible to electricity, with no solid waste.

Off Belgium, plans are in the works for 10 to 12 manufactured protective atolls, which would guard the coast from erosion as the sea rises. The idea is that the ocean, as it sluices in and out of the lagoons, runs through tidal turbines of the same sort already built into dikes in the Netherlands. This may be marine energy’s biggest advantage over other renewables in the coming century: it naturally piggybacks on the defense barriers that every coastal community is going to need as global warming bites in.

Gunter Pauli, the “ecopreneur” who has been called the Bill Gates of sustainable energy, initiated the first idea—those manufactured islands—and is kicking the tires on seaweed power as a natural adjunct to it. This is Pauli’s so-called “blue economy”—an interdependent network of energy choices driven by carefully integrated local supply chains and meeting local needs. Cluster technologies and suddenly you have not just green solutions—that might help revive the biodiversity of coastal zones, for instance—but a solid business model. “If you do tidal plus seaweed—a strange combination to most people, because it’s not solar plus wind—you have very interesting opportunities to supply a mix of local power,” Pauli says. “That is where the future lies. It’s not, ‘Oh, we’ve got the golden egg of this new energy source.’”

Another promising turn, in a way, is suspiciously familiar. Last fall, a wave-energy converter called the Hailong (Dragon) 1 appeared at a test facility in China. It is nearly identical to the Pelamis sea snake, right down to the paint color. The Guardian newspaper pressed the Chinese government for details about the origins of Hailong 1, but received no reply. Some former Pelamis employees privately worry that Pelamis might have done an awful lot of wave-energy and development work that the Chinese are now poised to make commercially viable.

Sad for the original creators, but perhaps good for everyone?

Marine energy will never be the new coal or oil—two fossil fuels that revolutionized the world. Where it could well shine, however, is in delivering power to the 40 percent of the world that has no reliable power now. Plus, marine energy could be combined with fertilizer, feed, and food—addressing global food-security issues, Pauli notes. Even the most eccentric schemes may have value so long as they are perfectly matched to their geography and put energy decisions into local hands.

On my last day in Orkney, I woke before dawn to pack for home. As I turned on the coffee maker in the hotel room, something occurred to me. A few kilometers away at the EMEC test site, a small OpenHydro tidal turbine was quietly supplying a trickle of energy to the island.

Since the machines in Fundy and Caithness were briefly offline, and I was up before just about everybody in France, I was enjoying a staggeringly exclusive experience. With perhaps a handful of Koreans, I was one of the only people in the world drinking coffee made from the power of the sea.

It tasted quite good.

*Shortly before publication of this story, Wavepower ceased operating.